package easy;

/**
 * Created by daodao on 2018/7/16.
 * Problem 70
 * Description: You are climbing a stair case. It takes n steps to reach to the top.
 * Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?
 *
 * Note: Given n will be a positive integer.
 *
 * Example 1: Input: 2
 *            Output: 2
 * Explanation: There are two ways to climb to the top.
 *              1. 1 step + 1 step
 *              2. 2 steps
 * Example 2: Input: 3
 *            Output: 3
 * Explanation: There are three ways to climb to the top.
 *              1. 1 step + 1 step + 1 step
 *              2. 1 step + 2 steps
 *              3. 2 steps + 1 step
 */
public class ClimbingStairs {
    public static int climbStairs(int n) {
        int[] dp = new int[n];
        dp[0] = 1;
        if (n > 1) {
            dp[1] = 2;
        }
        for (int i = 2; i < n; i++) {
            dp[i] = dp[i - 1] + dp[i - 2];
        }
        return dp[n - 1];
    }
}
